1. Field of the Invention
The present invention relates to shaft seals and is particularly concerned with automatic alignment of the rotating and stationary seal faces in a shaft seal.
2. Description of the Prior Art
The present invention relates to a family of seals which have been developed in order to overcome specific objections to seals heretofore offered in the seal industry.
Inasmuch as this the first disclosure of this family of seals, it is believed to be pertinent at this time to discuss the art, the drawbacks of the art and the resolutions of the problems heretofore encountered in the art.
The seal disclosed herein, and in fact the family of seals based thereon, are compatible with the various corrosive fluids being processed in the petroleum refining, petroleum transportation, high-pressure steam generation, high temperature, high pressure chemical production as well as other common mediums being proposed through centrifugal rotary pumps.
Metal components are preferably 316 and 316L stainless steel with the rotating face being primarily a P-658RC carbon with a stationary face of 99.5% alumina ceramic or silicon carbide. The O-rings will be of Viton.RTM. in temperature environments of -20.degree. F.-400.degree. F., or EPR in water solution and temperature environments of -65.degree. F.-+300.degree. F. (tetrafluorethylene can also be used where necessary to withstand corrosive effects chemical solutions which are injurious to synthetic rubber compounds). Typically, the stock sizes will range from 0.875" shaft to 4.750" shaft.
Some of the current problems being encountered with the state-of-the-art seals presently available on the market are:
(a) Shaft fretting by the rotating unit; PA1 (b) Installation of seals on shafts fretted or worn from previous use of packing; PA1 (c) Uneven face wear or leakage due to PA1 (d) Start-up-shutdown leakage and accelerated face wear due to thermo-distortion of the carbon faces, caused by the differential and thermal-expansion between the seal components with physical damage in the component configuration which results in the fact that the flat faces of the carbon element assuming a flat-convex-concave surface during changes in temperature and further resulting in progressive leakage, excessive P.V. values and excessive wear of the carbon face for each start-stop cycle; PA1 (e) Set screws for driving the rotational seal in the sleeve provide for uneven and tightening and can shift the seal off center or result in the sleeve being out of round causing the seal to rotate with a wiping action verses running a true concentric track and increasing the wear and the introduction of foreign matter between the faces.
Location of the secondary O-ring and anti-rotation lugs, and PA2 The torque applied to the seal faces during operation results in excursion of the seal face (wobble) resulting in the faces wearing conically, with excessive wear rate, with the introduction of foreign matter between the faces and excessive fretting on the O-ring surfaces arising;